Various agents are known to elicit modifications in the rumen fermentation pattern of ruminant animals. Certain of these modifications are utilized to effect improvements in growth rate or feed utilization efficiency in beef producing animals. However, of interest to the dairy industry would be an agent which, when administered to a lactating ruminant, would modify rumen fermentation in such a manner as to provide the animal with more energy and protein, the limiting factors in milk production. See, Clark and Davis, J. Dairy Sci., 63: 873-885 (1980) which is, as well as all other references alluded to herein, incorporated by reference.
The major sources of energy to the lactating ruminant are the ruminal volatile fatty acids (VFA's): acetic acid, propionic acid and butyric acid (alternatively referred to herein as acetate, propionate and butyrate, respectively). The VFA's are the metabolic end products of carbohydrate degradation in the rumen (carbohydrates represent an important nutrient in a typical ruminant feedstuff). It is known in the art that increasing the ruminal concentration of propionate without a depression of acetate or butyrate concentrations will lead to enhanced quality as well as quantity of milk produced inasmuch as each of these three major VFA's play a role in milk production. For example, acetate is required for milk fat synthesis. Propionate is utilized to produce glucose (which is a precursor for lactose synthesis), while butyrate is utilized for both lipogenesis and glycogenesis. See Hungate, The Rumen and its Microbes, Academic Press, New York, 1966. Hence, upon stimulation of all three VFA's, an increase in milk production will be observed without a decrease in milk fat content (reduced milk fat content leads to inefficient milk production due to a decreased quality and a consequent reduction in the commercial value of the milk). The digestive physiology of lactating ruminants is briefly reviewed in U.S. Pat. Nos. 4,376,790 and 4,336,250.
Protein concentration is also known to be a limiting factor in milk production. For instance, increased degradation of feed protein provides more ammonia and peptides for microbial growth. Stimulated microbial growth in the rumen provides greater amounts of amino acids for the animal. It has been reported that increased amino acid supply to the small intestine leads to increases in both the yield of milk as well as milk protein concentrations. Oldham and Parker, Process Biochemistry, page 30 et seq, Dec./Jan. 1980/81.